<!DOCTYPE html>

<html lang="en" data-content_root="../../">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />

    <title>Fingerprints and content hashes &#8212; Pytch  documentation</title>
    <link rel="stylesheet" type="text/css" href="../../_static/pygments.css?v=03e43079" />
    <link rel="stylesheet" type="text/css" href="../../_static/classic.css?v=36340f97" />
    <link rel="stylesheet" type="text/css" href="../../_static/css/pytch-classic.css?v=0321735e" />
    
    <script src="../../_static/documentation_options.js?v=7f41d439"></script>
    <script src="../../_static/doctools.js?v=9bcbadda"></script>
    <script src="../../_static/sphinx_highlight.js?v=dc90522c"></script>
    
    <link rel="icon" href="../../_static/favicon.ico"/>
    <link rel="author" title="About these documents" href="../../about.html" />
    <link rel="index" title="Index" href="../../genindex.html" />
    <link rel="search" title="Search" href="../../search.html" />
    <link rel="next" title="Linked content for a project" href="linked-content.html" />
    <link rel="prev" title="Media Library" href="assets-library.html" /> 
  </head><body>
<div class="NavBar">
  <a href="../../../app/"><h1>Pytch</h1></a>
  <ul>
    <a href="https://pytch.scss.tcd.ie/"><li>About Pytch</li></a>
    <a href="../../index.html"><li>Help</li></a>
    <a href="../../../app/tutorials/"><li>Tutorials</li></a>
    <a href="../../../app/my-projects/"><li>My projects</li></a>
  </ul>
</div>
<div class="warning-work-in-progress">
  <p>These help pages are incomplete — we are working on it!</p>
</div>
  

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body" role="main">
            
  <section id="fingerprints-and-content-hashes">
<h1>Fingerprints and content hashes<a class="headerlink" href="#fingerprints-and-content-hashes" title="Link to this heading">¶</a></h1>
<p>These terms are similar, but have distinct meanings in the codebase:</p>
<dl class="simple">
<dt>Fingerprint</dt><dd><p>A string of text computed from an object such that if two objects
have the same fingerprint, those objects have the same content.
(Well, except for hash collisions.)</p>
</dd>
<dt>Content hash</dt><dd><p>The lower-case hexadecimal representation of a SHA256 hash (of some
input related to the object, often its fingerprint.)</p>
</dd>
</dl>
<section id="example">
<h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>
<p>The fingerprint of a <code class="docutils literal notranslate"><span class="pre">&quot;flat&quot;</span></code> project is a string of the form</p>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>program=flat/272b26e4f3edbdf5586bae5d83fe9d24b93a8df77c60c774a82f963dbcff61b8
assets=8c87⋯f254/9648⋯01bd/ecfe⋯8f37/fa7a⋯bd28
</pre></div>
</div>
<p>The content-hash of a project is the SHA256 sum of its fingerprint.</p>
<p>See the code for the details of what goes into the two parts of a
project’s fingerprint.</p>
</section>
</section>


            <div class="clearer"></div>
          </div>
        </div>
      </div>
      <div class="sphinxsidebar" role="navigation" aria-label="Main">
        <div class="sphinxsidebarwrapper"><ul class="current">
<li class="toctree-l1"><a class="reference internal" href="../user/index.html">Using the Pytch web app</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../vm/user/index.html">Writing Pytch programs</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../about.html">About Pytch</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../contact.html">Contact</a></li>
<li class="toctree-l1 current"><a class="reference internal" href="../../developer.html">Developer documentation</a><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="../../developer/development-setup.html">Development setup</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../developer/design-overview.html">Design overview</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../vm/developer/index.html">VM</a></li>
<li class="toctree-l2 current"><a class="reference internal" href="index.html">Webapp</a><ul class="current">
<li class="toctree-l3"><a class="reference internal" href="index.html#top-level-routes">Top-level routes</a></li>
<li class="toctree-l3 current"><a class="reference internal" href="index.html#individual-aspects-of-design">Individual aspects of design</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../../medialib/developer/index.html">Media library</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../developer/index.html">Website</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../build-tools/index.html">Tools</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../source-build.html">Source and build information</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../releases/changelog.html">Changelog</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../../legal/index.html">Legal information</a></li>
</ul>
<div class="docs-home-link"><hr>
  <ul>
    <li>
      <a href="../../index.html">Pytch help home</a>
    <li>
  </ul>
</div>
        </div>
      </div>
      <div class="clearer"></div>
    </div>
  </body>
</html>